No. PCIe is essentially a multi-channel 1 to 1 serial bus. Multiplexing those serial channels is possible with hardware and drivers but I know of no off the shelf product to do so. Only seen in on motherboards to "share" channels between ancillary devices like USB 3 controllers and PCIe ethernet chips."Life is just nature's way of keeping meat fresh." - The Doctor

The best way to get two cards in one PCIe slot is to do what Tom told you, get one card that has two gpu on it. It will cost you premium, probably going to need to get a new power supply to power that beast, but that is the smart way to get two gpu in one PCIe slot.

My tip, is possible, but don´t try do that, is safer and cheap buy a better MB with more slots or build a second host.

Even the factory made double GPU´s have some limitations (i have few 590/690 so i know wath i´m talking) imagine a "band-aid" solution.

We do something similar by ussing a PCI-extensors in order to put more GPU´s on the same MB (but still 1 GPU per slot), works but in the end all goes to complicated and the entire system easely crashes, and when works all the PCI-e slots works extreamely slow, so the actual performance decrases exponentialy.

Lets you connect a PCI-e card into an old PCI slot. It means the card only communicates at PCI speed, but for SETI work that's not a fatal problem. If I remember right another cruncher has tried them and found less than 10% performance loss.

Of course putting the lid back on the PC may be an issue, but shoe horning 2 cards into one slot is going to cause that sort of issue anyway.

Lets you connect a PCI-e card into an old PCI slot. It means the card only communicates at PCI speed, but for SETI work that's not a fatal problem. If I remember right another cruncher has tried them and found less than 10% performance loss.

Of course putting the lid back on the PC may be an issue, but shoe horning 2 cards into one slot is going to cause that sort of issue anyway.

Ian

I could confirm, this works i try before, but you made your 16x card run in a 1x slot, and yes not a totaly dissaster if you run SETI but some misterious "hangs" happens when running, never realy find why, all my tests point in the direction of hidden mechanical incompatibilites and/or electric faulty conections (like some spikes in the PCI-e slot due the high frequency), normaly cleared after reboot.

If you want to try just keep in mind if your GPU drain power (not all do that) from the PCI-e there is a 75W limit on all devices, or you will literaly "melt" your 12V connectors on your MB.